Using the Derivative of a Function.
A mass hanging from a vertical spring is in simple harmonic motion as given by the following position function, where $t$ is measured in seconds and $s$ is in inches
For $t > 0$, determine the first two times at which the velocity of the spring is zero.
Type answer in form $t = c$. Separate multiple answers with a comma, such as $t = 1, t = -1$
$s(t) = -3 \cos(\pi t + \frac{\pi}{6})$
